Annubis, from your viewing of the original Orguss, it sounds like you'd like Yoshiyuki Tomino's less popular anime, but cool mecha designs in Aura Battler Dunbine. It's not Gundam or Macross, but you can def. see those similarities in the obscurity of a lost world, biological concepts, and cool mecha designs. ADV put out a boxset many years back, but I don't know if you can find the set nowadays.
I did love the follow up to Orguss in Orguss 02. I watched that OAV over and over on VHS in the mid-late 90's before DVDs became the next big thing in the early 00's. Plus Orguss 02 had one of the coolest openings to an OAV anime I've ever seen.